Muscle Adaptations to High-Load Training and Very Low-Load Training With and Without Blood Flow Restriction

Abstract

An inability to lift loads great enough to disrupt muscular blood flow may impair the ability to fatigue muscles, compromising the hypertrophic response. It is unknown what level of blood flow restriction (BFR) pressure, if any, is necessary to reach failure at very low-loads [i.e., 15% one-repetition maximum (1RM)]. The purpose of this study was to investigate muscular adaptations following resistance training with a very low-load alone (15/0), with moderate BFR (15/40), or with high BFR (15/80), and compare them to traditional high-load (70/0) resistance training. Using a within/between subject design, healthy young participants (n = 40) performed four sets of unilateral knee extension to failure (up to 90 repetitions/set), twice per week for 8 weeks. Data presented as mean change (95% CI). There was a condition by time interaction for 1RM (p < 0.001), which increased for 70/0 [3.15 (2.04,4.25) kg] only. A condition by time interaction (p = 0.028) revealed greater changes in endurance for 15/80 [6 (4,8) repetitions] compared to 15/0 [4 (2,6) repetitions] and 70/0 [4 (2,5) repetitions]. There was a main effect of time for isometric MVC [change = 10.51 (3.87,17.16) Nm, p = 0.002] and isokinetic MVC at 180°/s [change = 8.61 (5.54,11.68) Nm, p < 0.001], however there was no change in isokinetic MVC at 60°/s [2.45 (−1.84,6.74) Nm, p = 0.261]. Anterior and lateral muscle thickness was assessed at 30, 40, 50, and 60% of the upper leg. There was no condition by time interaction for muscle thickness sites (all p ≥ 0.313). There was a main effect of time for all sites, with increases over time (all p < 0.001). With the exception of the 30% lateral site (p = 0.059) there was also a main effect of condition (all p < 0.001). Generally, 70/0 was greater. Average weekly volume increased for all conditions across the 8 weeks, and was greatest for 70/0 followed by 15/0, 15/40, then 15/80. With the exception of 1RM, changes in strength and muscle size were similar regardless of load or restriction. The workload required to elicit these changes lowered with increased BFR pressure. These findings may be pertinent to rehabilitative settings, future research, and program design.

Low‐Load Resistance Training With Blood‐Flow Restriction in Relation to Muscle Function, Mass, and Functionality in Women With Rheumatoid Arthritis

“…Because the patients were women, sedentary (with ~60% sedentary time per day), postmenopausal, fairly functional, and in remission or with mild‐to‐moderate disease activity, these data cannot be extrapolated to patients with different characteristics (e.g., those with a more severe disease). Because we opted for 1RM reassessments throughout the training protocol, one might consider those as supplemental high‐load training sessions, possibly affecting strength gains . However, in the current study, in addition to the control group, the other 2 groups also had multiple familiarization sessions before beginning the trial, and only 2 reassessments were conducted during training (at weeks 4 and 8), which is far less than previously shown to affect strength, thus mitigating a possible confounding effect and strengthening the current design.…”

Exercise-Induced Changes in Muscle Size do not Contribute to Exercise-Induced Changes in Muscle Strength

“…To illustrate, studies implementing body weight exercise have found increases in muscle size but not necessarily changes in voluntary strength [16,17]. This is corroborated by two additional studies with very low load resistance exercise where muscle growth appeared to change but strength in the task they were training did not [18,19]. When considered together, there is strong evidence that muscle growth is not necessary for an increase in strength and some evidence that muscle growth is also not sufficient for an increase in strength.…”

The Generality of Strength Adaptation

“…24 Insight into the generality of strength adaptation can also be gained from the low load training literature. Jessee et al 25 noted a 10% increase in isotonic knee extensor 1RM strength following isotonic training at moderate training load (70% 1RM). The study also included three very-low load training conditions (15% 1RM with and without blood flow restriction) that observed no meaningful changes in isotonic knee extensor strength.…”